1. Field
The present disclosure relates generally to communication systems, and more particularly, to apparatus and methods for service acquisition when moving in and out of fourth generation (4G) networks with different circuit-switched fallback (CSFB) support.
2. Background
Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power). Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.
These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example of an emerging telecommunication standard is Long Term Evolution (LTE). LTE is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by Third Generation Partnership Project (3GPP). It is designed to better support mobile broadband Internet access by improving spectral efficiency, lower costs, improve services, make use of new spectrum, and better integrate with other open standards using OFDMA on the downlink (DL), SC-FDMA on the uplink (UL), and multiple-input multiple-output (MIMO) antenna technology.
CSFB is a technique that delivers voice-services to a user equipment (UE) when the UE is camped in an LTE network but the LTE network does not support voice services natively. Currently, when a UE that is required to support voice service determines that an available LTE or 4G network does not support CSFB, in order to avoid disruption in voice services, the UE inhibits operating according to LTE and only reports second generation (2G) and/or third generation (3G) capability. In this case, the UE may later resume supporting LTE at the time of the next power on/off cycle of the UE, but loses 4G access until then even if, before that next power on/off cycle, the UE moves to an LTE network that does support CSFB.
As the demand for mobile broadband access continues to increase, there exists a need for further improvements in LTE technology. Preferably, these improvements should be applicable to other multi-access technologies and the telecommunication standards that employ these technologies. Thus, in this case, improved service acquisition is desired for 4G-capable UEs moving in and out of 4G networks with different CSFB support.